The present invention relates to a zero valent metal composite, a method for manufacturing thereof, a method using thereof, a system including thereof, and an article-of-manufacture including thereof. The zero valent metal composite is used for (in-situ or ex-situ) catalytically treating contaminated water. The present invention is generally applicable to (in-situ or ex-situ) catalytically treating any of a wide variety of different forms of contaminated water, for example, sub-surface water, surface water, above-surface water, water vapor, gaseous water, or any combination thereof, which are contaminated with any number of a wide variety of different types or kinds of organic or/and inorganic chemical contaminants. The present invention is particularly applicable to (in-situ or ex-situ) catalytically treating such forms of contaminated water wherein the water contaminants are organic species, for example, halogenated organic compounds and halogen containing degradation products thereof; inorganic species, for example, metal elements, metal element containing inorganic species, nonmetal elements, and nonmetal element containing inorganic species; or any combination thereof. The present invention is also applicable to (in-situ or ex-situ) catalytically treating contaminated non-aqueous fluids (in liquid, vapor, or/and gaseous forms), for decreasing contaminant concentrations therefrom.
Herein, in the context of the field and art of the present invention, it is to be fully understood that the terms ‘contaminated’ and ‘polluted’ are synonymous and equivalent to each other, and for consistency, the term ‘contaminated’ is generally used. Accordingly, the phrases ‘contaminated water’ and ‘polluted water’ are synonymous and equivalent to each other, and, for consistency, the term ‘contaminated water’ is generally used. Additionally, herein, it is to be fully understood that the terms ‘contaminant(s)’ and ‘pollutant(s)’ are synonymous and equivalent to each other, and, for consistency, the term ‘contaminant(s)’ is generally used.
Contaminated Water, and Forms Thereof:
In general, in the context of the field and art of the present invention, contaminated water can be any of a variety of numerous different forms. Exemplary general forms of contaminated water, which are particularly relevant to the field and art of the present invention, are sub-surface water, surface water, above-surface water, water vapor, gaseous water, and combinations thereof, which contain chemical contaminants.
Sub-surface water is to be understood as generally being water which is ‘entirely’ located below or beneath the ground or earth. Exemplary specific forms of sub-surface water, which are particularly relevant to the field and art of the present invention, are, typically naturally existing, but possibly human made or/and formed, ground water (i.e., water found underground beneath the earth's surface within partially or fully saturated soil or/and porous rock), water of an aquifer (i.e., a water-bearing rock or rock formation, or an underground layer of porous rock, sand, etc., containing water), wells or springs (i.e., flows of water from the ground or earth), rivers, streams, lakes, ponds, pools, or sub-surface water reservoirs, which are entirely located below or beneath the ground or earth. Additional exemplary specific forms of sub-surface water, which are also relevant to the field and art of the present invention, are water that is, or/and may be, present or contained in human made (commercial size) large volume water receiver, collection, or/and storage, vessels, containers, reservoirs, or chambers, which are entirely located below or beneath the ground or earth.
Surface water is to be understood as generally being water whose top or uppermost surface is located at about ground or earth level. Typically, but not necessarily, the top or uppermost surface of surface water is exposed to air or the atmosphere under the sky (i.e., not beneath or below the ground). Exemplary specific forms of surface water, which are particularly relevant to the field and art of the present invention, are, typically naturally existing, but possibly human made or/and formed, rivers, streams, lakes, ponds, pools, surface water reservoirs, or, wells or springs, each of whose top or uppermost surface is located at about ground or earth level. Additional exemplary specific forms of surface water, which are also relevant to the field and art of the present invention, are water that is, or/and may be, present or contained in human made (commercial size) large volume water receiver, collection, or/and storage, vessels, containers, reservoirs, or chambers, which are located at about ground or earth level.
Above-surface water is to be understood as generally being water whose top or uppermost surface is located above ground or earth level. Exemplary specific forms of above-surface water, which are particularly relevant to the field and art of the present invention, are, typically human made or/and formed, but possibly naturally existing, above-surface water reservoirs, or, above-surface sources or supplies of residential or commercial drinking, each of whose top or uppermost surface is located above ground level. Additional exemplary specific forms of above-surface water, which are also relevant to the field and art of the present invention, are water that is, or/and may be, present or contained in human made (commercial size) large volume water receiver, collection, or/and storage, vessels, containers, reservoirs, or chambers, which are located above ground or earth level.
Water vapor is to be understood as generally being water existing as a vapor, i.e., as a barely visible or cloudy diffused form of water, such as water mist, water fumes, or steam, suspended in air. Gaseous water is to be understood as generally being water existing in the gas phase. Such water vapor or/and gaseous water exists as either a pure vapor or/and gas of water, or as part of a vapor or/and gas mixture which also includes other vapor or/and gaseous species.
In a non-limiting manner, in the context of the field and art of the present invention, it is to be understood that the contaminated water can be of a form corresponding to a combination of any two or more of the above stated exemplary general forms, of water, i.e., sub-surface water, surface water, above-surface water, water vapor, and gaseous water, and exemplary specific forms thereof, which contain chemical contaminants.
In general, in the context of the field and art of the present invention, any of the preceding described forms of contaminated water, in addition to the undesirable chemical contaminants, may contain, typically naturally existing, but possibly human made or/and formed, ground or earth types or kinds of geological matter. Exemplary specific ground or earth types or kinds of geological matter, which are particularly relevant to the field and art of the present invention, are soil, sand, rocks, stones, pebbles (i.e., small rocks or stones), sediment (i.e., matter deposited by water or wind), fragments thereof, or any combination thereof (e.g., gravel, being an unconsolidated combination (mixture) of rock fragments or pebbles).
Such ground or earth types or kinds of geological matter are typically present in the immediate environment or ecosystem surrounding or encompassing sub-surface and surface forms of water. In fact, by definition, each of the various different forms of sub-surface water, for example, ground water (i.e., water found underground beneath the earth's surface within partially or fully saturated soil or/and porous rock), water of an aquifer (i.e., a water-bearing rock or rock formation, or an underground layer of porous rock, sand, etc., containing water), wells or springs (i.e., flows of water from the ground or earth), rivers, streams, lakes, ponds, pools, or sub-surface water reservoirs, which are entirely located below or beneath the ground or earth, are surrounded or encompassed by immediate environments or ecosystems within which are present the above stated ground or earth types or kinds of geological matter.
Similarly, by definition, each of the various different forms of surface water, for example, rivers, streams, lakes, ponds, pools, surface water reservoirs, or, wells or springs, each of whose top or uppermost surface is located at about ground or earth level, are surrounded or encompassed by immediate environments or ecosystems within which are present the above stated ground or earth types or kinds of geological matter.
Types or Kinds of Water Contaminants:
In the context of the field and art of the present invention, a water contaminant is to be understood as generally being a chemical specie (atom, ion, radical, molecule) that is proven or known, or suspected, as being hazardous (poisonous or toxic), or potentially hazardous, to a human or animal subject. Accordingly, in the context of the field and art of the present invention, the phrase ‘contaminated water’ is to be understood as generally being water which contains or includes at least one chemical specie (atom, ion, radical, molecule) that is/are proven or known, or suspected, as being hazardous (poisonous or toxic), or potentially hazardous, to a human or animal subject.
In general, in the context of the field and art of the present invention, any of the above described forms of contaminated water may contain any number of a wide variety of different types or kinds, and forms, of contaminants. In general, water contaminants can be characterized as being composed of organic (carbon containing) species (atoms, ions, radicals, molecules), inorganic species (atoms, ions, radicals, molecules), or any combination thereof.
In a non-limiting manner, exemplary specific types or kinds of water contaminants composed of organic species, which are particularly relevant to the field and art of the present invention, are aromatic organic compounds (i.e., aromatic hydrocarbons, or arenes), and non-aromatic organic compounds (i.e., non-aromatic hydrocarbons, aliphatic hydrocarbons (alkanes), or conjugated hydrocarbons (alkenes, alkynes). An aromatic organic compound (aromatic hydrocarbon, or arene) type or kind of water contaminant may contain at least one halogen atom (i.e., fluorine [F], chlorine [Cl], bromine [Br], or/and iodine [I]. Similarly, a non-aromatic organic compound (non-aromatic hydrocarbon, aliphatic hydrocarbon, or conjugated hydrocarbon) type or kind of water contaminant may contain at least one halogen atom (i.e., fluorine [F], chlorine [Cl], bromine [Br], or/and iodine [I]. Accordingly, any such halogen containing aromatic organic compound or halogen containing non-aromatic organic compound may be mono-halogenated or poly-halogenated. Such halogen containing aromatic organic compounds and halogen containing non-aromatic organic compounds are generally referred to as halogen containing organic compounds, or, synonymously and equivalently, as halogenated organic compounds. Moreover, an aromatic organic compound or non-aromatic organic compound type or kind of water contaminant may contain at least one heteroatom (e.g., nitrogen [N], oxygen [O], sulfur [S], or/and phosphorous [P].
In a non-limiting manner, exemplary specific types or kinds of halogenated organic compound water contaminants which are especially relevant to the field and art of the present invention, are methylene chloride, chloroform, carbon tetrachloride, trichloroethane, di-, tri-, and tetra-chloroethylenes, polychlorinated biphenyls, tribromoneopentlyalcohol (TBNPA), and halogen containing degradation products thereof.
In a non-limiting manner, exemplary specific types or kinds of water contaminants composed of inorganic species, which are particularly relevant to the field and art of the present invention, are metal elements, metal element containing inorganic species, nonmetal elements, and nonmetal element containing inorganic species.
Exemplary metal elements are transition metal elements, inner transition metal elements, and non-transition metal elements. Exemplary transition metal elements are zinc [Zn], cadmium [Cd], chromium [Cr], manganese [Mn], molybdenum [Mo], vanadium [V], iron [Fe], cobalt [Co], nickel [Ni], copper [Cu], silver [Ag], tungsten [W], and technetium [Tc]. Exemplary inner transition metal elements are uranium [U], plutonium [Pu], cesium [Cs]. Exemplary non-transition metal elements are lead [Pb], tin [Sn], antimony [Sb], aluminum [Al], strontium [Sr], and radium [Ra]. In general, any of the above metal elements is in a neutral (elemental, or zero valent) form, or in a charged (cationic) form. Moreover, any of the above metal elements may be a radionuclide, such as technetium-99 [Tc-99], cesium-137 [Cs-137], strontium-90 [Sr-90], and radium-226 [Ra-226].
Exemplary nonmetal elements are arsenic [As], and selenium [Se]. In general, the nonmetal element is in a neutral (elemental, or zero valent) form, or in a charged (cationic) form.
Exemplary nonmetal element containing inorganic species are oxygen containing inorganic species. Exemplary oxygen containing inorganic species are oxygen containing ions (also known as oxyions, or as oxo-anions). Exemplary oxygen containing ions are borate ions, nitrate ions, sulfate ions, phosphate ions, halogenate ions (i.e., containing a halogen), and metal oxide ions.
On-going Problem of Water Contaminated with Halogenated Organic Compounds:
Among the wide variety of the above described different types or kinds of water contaminants, halogenated (especially, chlorinated) organic compounds are arguably the most common, pervasive (widespread), persistent (e.g., having half-lives ranging from days to 10,000 years), proven or potentially hazardous (poisonous or toxic), undesirable contaminants in various forms of water, such as sub-surface water, surface water, above-surface water, water vapor, gaseous water, and combinations thereof, which contain contaminants. Many such forms of water are, or/and come in direct contact with, or/and lead to, sources of drinking water. Currently, numerous halogenated (especially, chlorinated) organic compounds are still being applied in large quantities on large scales, in a wide variety of different agricultural and other industrial processes, by exploiting their high performance, in addition to their relatively high stability and resistance to chemical and biological degradation. It is now recognized that these properties, which are essential to agriculture and other industries, have devastating effects on the environment, translating to undesirable short and long term health problems.
The fate of anthropogenic (human originating or synthesized) halogenated organic compound contaminants in the environment is of great concern because of their proven or potential proven or potentially hazardous (poisonous or toxic) properties and characteristics. Discharge of these compounds into sub-surface, surface, or/and above-surface, water containing environments has led to extensive water contamination. Largely based on the fact that sub-surface water (for example, ground water, water of an aquifer, wells or springs, rivers, streams, lakes, ponds, pools, or sub-surface water reservoirs, which are entirely located below or beneath the ground or earth) account for about 95% of the earth's usable fresh water resources, sub-surface water contamination is particularly a critical issue. Intensive efforts are continuously being invested in the development of improved and new technologies for treating or remediating sub-surface water, surface water, or/and above-surface water, contaminated with halogenated organic compounds.
Carbon tetrachloride (CT) is an exemplary widespread water contaminant, used mostly in the production of refrigeration fluids and propellants, and has the potential to cause cancer after long-term exposure to a maximum contaminant level (MCL), corresponding to a maximum allowable concentration, established by the Safe Drinking Act as being safe for human health and the environment, of 5 ppb. From 1987 to 1993, according to the Toxic Release Inventory of the US Environmental Protection Agency (US EPA), releases of CT to the environment totaled nearly 76,000 pounds. Perchloroethylene, in particular, tetrachloroethylene (PCE) and trichloroethylene (TCE) are solvents widely used for dry cleaning and metal degreasing, and can be found in household products. Their maximum contaminant level (MCL) is 5 ppb. Both PCE and TCE were found to have toxic effects on humans and are considered as potential carcinogenic substances. According to the US EPA Toxic Chemical Release Inventory, releases of PCE and TCE to land and water from 1987 to 1993 totaled over 1 million pounds, and about 300,000 pounds, respectively. PCE and TCE are present in at least 771 of 852 National Priority List sites identified by the US EPA. It has been shown [1] that 130 liters (about 0.6 drum) of the organic contaminants trichloroethane (TCA), 1,1-dichloroethylene (1,1 D CE), and Freon 113, were sufficient to pollute 5,000,000,000 liters of water in San Jose, Calif. Similarly, a release of 1500 liters (about 7 drums) of TCE, PCE, and detergents, contaminated 40,000,000,000 liters of water in Cape Cod, Mass.
In spite of proven and potential environmental and health hazards, many halogenated compounds, among the wide variety of different types of persistent water contaminants, currently remain in widespread international use, thereby perpetuating a continuously on-going problem. The main concern lies in the large quantities of persistent contaminants, and their degradation products, present in, or in close proximity to, forms of water which either are, or lead to, sources of water to which humans or/and animals are directly or indirectly exposed.
Current Techniques, and Limitations Thereof, for Treating or Remediating Contaminated Water:
Although not a technique per se for treating or remediating the above stated forms of contaminated water, the concept or principle of ‘natural attenuation’ is currently practiced for attempting to achieve or accomplish such treatment or remediation. ‘Natural attenuation’ (NA) generally refers to the natural occurrence or taking place of any number of various different physical, chemical, or/and biological types of natural phenomena, mechanisms, and processes, for example, involving degradation, transformation, conversion, sorption, among others, which under favorable conditions cause or lead to ‘natural’ reduction or attenuation of various quantifiable parameters or properties, such as mass, toxicity, mobility, volume, or/and concentration, of contaminants in contaminated water.
A main limitation of practicing natural attenuation (NA) is based on the fact that it essentially entirely depends upon ‘naturally’ reducing or attenuating the various quantifiable parameters or properties, such as mass, toxicity, mobility, volume, or/and concentration, of the water contaminants in the contaminated water. Meaningful natural attenuation can require time periods of on the order of years, thus accounting for the relatively long persistence of water contaminants in contaminated water.
In particular cases where the contaminated water is a form of sub-surface water, for example, ground water, water of an aquifer, well or spring, pond, pool, or sub-surface water reservoir, which is entirely located below or beneath the ground or earth, then, by practicing natural attenuation, long time periods of continuous underground water flow are often required for the various quantifiable parameters or properties of the water contaminants, and possible degradation products, to be sufficiently decreased or attenuated in the underground water. In contrast to river water, which has a turnover time on the order of two weeks, such forms of sub-surface water have residence times on the order of about 2 weeks to about 10,000 years. Additionally, the large horizontally or/and vertically extending, and heterogeneous, contaminant zones or regions (contaminant plumes) of underground water types of water contaminants tend to be very difficult to locate, detect, characterize, and treat or remediate.
Aside from the continued practice of ‘natural attenuation’, there exists a plethora of numerous different types of well known and used prior art techniques (methods, materials, compositions, devices, and systems) for treating or remediating contaminated water, where the contaminated water is a form of sub-surface water, surface water, above-surface water, water vapor, gaseous water, or any combination thereof. Each particular technique is primarily based on principles, phenomena, mechanisms, and processes, in one of the following main categories: (a) physical/physical chemical, (b) biological, or (c) chemical. A common ultimate objective of each water treatment or remediation technique is to in-situ or/and ex-situ eliminate, or at least decrease, concentrations of the hazardous (poisonous or toxic) or potentially hazardous water contaminants, and desirably, also, any of their degradation products, in the contaminated water.
The scope of the present invention encompasses treating contaminated water, wherein the contaminated water is, for example, a form of sub-surface water, surface water, above-surface water, water vapor, gaseous water, or any combination thereof. For the purpose of providing exemplary background, following are brief descriptions of the above categorized techniques, along with selected examples of prior art teachings thereof, for treating or remediating contaminated water.
(a) Physical/Physical Chemical Techniques for Treating or Remediating Contaminated Water:
Physical/physical chemical techniques for treating or remediating contaminated water are based on exploiting physical or physicochemical types of phenomena, mechanisms, and processes. Exemplary prior art physical/physical chemical techniques for treating or remediating contaminated water are: air stripping, and air sparging, whereby a forced flow of air is used for moving or transporting, and removing, water contaminants from contaminated water; filtration, whereby a filter medium or substrate is used for absorbing, adsorbing, and removing, water contaminants from contaminated water; and chemical destruction (without chemical reagents), whereby extreme conditions of temperature or/and pressure are used for breaking chemical bonds of water contaminants in contaminated water. In each technique, water contaminants are ‘physically’ or ‘physicochemically’ moved or transported, and removed, from contaminated water to another medium, such as air, or a filter, or are degraded, transformed, or/and converted, in the contaminated water to non-hazardous or/and less hazardous species.
Air stripping, as an exemplary physical/physical chemical technique for treating or remediating contaminated water, is based on physically transferring volatile water contaminants from contaminated water into air. Air stripping is considered a ‘pump and treat’ type of technique. Contaminated water is pumped into a tank containing packing material. The contaminated water trickles down through spaces between the packing material towards the bottom of the tank, while at the same time a fan operating at the bottom of the tank blows and forces air upward. Forced air upwardly passing through the contaminated water and between the packing material causes volatile water contaminants to evaporate out from the top of the tank, thereby removing the water contaminants from the contaminated water.
Air sparging, as another exemplary physical/physical chemical technique for treating or remediating contaminated water, is based on injecting air directly into contaminated water. Injected air passing through the contaminated water physically contacts and removes water contaminants from the contaminated water. The water contaminants become partitioned between the contaminated water and the passing air, according to Henry's law, and are subsequently moved or transported, and removed, from the contaminated water to another zone or region. For example, in the case of ground water, to a zone or region of soil unsaturated with contaminated water. As the water contaminants are driven or diffused to the unsaturated zone or region, a soil vapor extraction system is usually used to remove water contaminant vapors. The addition of oxygen to contaminated ground water and soils also enhances biodegradation, as the oxygen acts as a nutrient for bacteria.
Filtration, as another exemplary physical/physical chemical technique for treating or remediating contaminated water, is based on activated carbon filtration. Typically, a carbon filter is used for this technique. A typical activated carbon filter is made of tiny clusters of carbon atoms, in the bulk form of granular or powder sized particles derived from any number of various sources, creating a highly porous and active material with an extremely high surface area for contaminant adsorption. The contaminated water is exposed to the activated carbon filter, during which the water contaminants diffuse and are adsorbed by, and become concentrated on, the activated carbon, and are thereby removed from the contaminated water. After significant build up of the water contaminants on the activated carbon, the water contaminant containing de-activated carbon filter is removed from the contaminated water, and disposed of, or, flushed or otherwise treated (regenerated) to remove the water contaminants and re-activate the carbon for re-use.
Each of the above described air stripping, air sparging, and filtration, techniques has limitations for treating or remediating contaminated water. Air stripping and air sparging techniques are effective only for relatively large concentrations (over 100 ppm) of volatile contaminants. Both techniques merely move or transfer water contaminants from the contaminated water to the air, without degrading, transforming, or/and converting, the water contaminants to non-hazardous or/and less hazardous environmentally acceptable species. Similarly, a significant limitation of the filtration technique is that water contaminants are essentially only transferred from the contaminated water to the filter medium or substrate, without being degraded, transformed, or converted, to non-hazardous or/and less hazardous environmentally acceptable species. Additionally, implementation of this technique requires resources (manpower and equipment) for removing, and disposing of, or, regenerating, the de-activated filter medium or substrate which is contaminated with the water contaminants.
Chemical destruction (without chemical reagents), as another exemplary physical/physical chemical technique for treating or remediating contaminated water, is based on using machine generated extreme or destructive conditions of temperature or/and pressure, in the absence of destructive chemical reagents, for breaking chemical bonds of the water contaminants, for the objective of destroying the water contaminants. Destruction of the water contaminants may involve degrading, transforming, or/and converting, the water contaminants to non-hazardous or/and less hazardous species. Such a technique has been proposed [2] for degrading atrazine
(being an exemplary halogenated organic compound) under high temperature (150-200° C.) and pressure (3.0-6.0 MPa).
A first significant limitation of using the technique of chemical destruction (without chemical reagents) for treating or remediating contaminated water is that the machine generated extreme conditions (typically, high temperatures or/and pressures) are relatively difficult and expensive to apply to large (areal or/and volumetric) scale forms of contaminated water. A second significant limitation of this technique is that use of the machine generated extreme conditions may be accompanied by undesirable consequences, such as partial or complete change of the immediate environment or ecosystem, and geological matter present therein, surrounding or encompassing the form of contaminated water being treated. This is particularly problematic if the form of contaminated water is surrounded or encompassed by a naturally existing environment or ecosystem.
(b) Biological Techniques for Treating or Remediating Contaminated Water:
Biological techniques for treating or remediating contaminated water are based on exploiting biological (microbiological) types of phenomena, mechanisms, and processes, involving the use of biological organisms (such as microbes, microorganisms, bacteria), for ‘biologically’ degrading, transforming, converting, or/and immobilizing, the water contaminants in the contaminated water to non-hazardous or/and less hazardous species.
It is well known that different types of biological microorganisms are effective for treating water contaminated with halogenated organic compounds. For example, anaerobic type microorganisms are known for being able to degrade, transform, or/and convert, a wide variety of halogenated organic compounds. Important advantages of using microorganisms are that the process of dehalogenation (especially, dechlorination) occurs in-situ, and the compounds are typically completely degraded, transformed, or/and converted, thereby precluding the need for using another method for degrading intermediate degradation products of the halogenated organic compounds. However, a significant limitation of using microbiological techniques for treating contaminated water is that, typically, they are strongly influenced, and may be inactivated, by changes in environmental conditions, such as pH, temperature, or/and nutrient supply, which take place during the water treatment, especially during long term water treatment.
Another significant limitation of using microbiological systems for treating water contaminated with halogenated organic compounds is that high contaminant concentrations can be poisonous or toxic to the contaminant degrading bacteria. For example, it has been shown [3] that during dechlorination of trichloroethylene (TCE) and vinyl chloride (VC), acetylene is an abiotically formed intermediate species which can inhibit the biotic transformation, conversion, or degradation, of the initial halogenated organic compound contaminants.
Origin and Main Processes of Sub-surface Water Contamination:
Any given prior art technique for treating or remediating contaminated water, in general, and contaminated sub-surface water, in particular (e.g., ground water, water of an aquifer, well or spring, pond, pool, or sub-surface water reservoir), contaminated with organic compound contaminants, typically has any number and types of advantages and disadvantages, depending upon the actual properties, parameters, characteristics, types and forms, and behavior, of the water contaminants, and of the sub-surface water. Before describing specific problems and limitations of current techniques which are particularly problematic, and difficult to overcome, for treating or remediating contaminated sub-surface water, in addition to those already described hereinabove, it is useful to first briefly describe the origin and main processes of sub-surface water contamination.
Following exposure of the ground or earth to chemical wastes (i.e., contaminants), particularly involving a wide variety of numerous different types or kinds of industrial or commercial processes, then, eventually, occurrence of any number and types or kinds of natural processes, such as formation of moisture (i.e., from the air or atmosphere), dew, rain, snow, or/and sleet, or/and, occurrence of human or/and machine generated processes, such as watering, or/and irrigating, among others, result in wetting the ground or earth (including the chemical wastes (contaminants) thereupon). Thereafter, the water soluble and mobile chemical wastes (contaminants), and possible initial degradation products thereof, become dissolved, transported, and, as a result of various diffusion, adsorption, desorption, and mass transfer processes, become heterogeneously distributed into, throughout, and among, various different horizontally or/and vertically extending zones or regions of the above stated types and forms of sub-surface water.
Such zones or regions of the different forms of sub-surface water begin at, and extend to, varying depths below or beneath the top or uppermost surface layer of the ground or earth. For example, such zones or regions of sub-surface water typically begin from a depth of about 5 centimeters, and can extend to a depth of about 2000 meters, below or beneath the top or uppermost surface layer of the ground or earth. In the particular case where the sub-surface water is a form of ground water, water of an aquifer, well or spring, pond, pool, or sub-surface water reservoir, then, dissolution, transport, and heterogeneous distribution, of the chemical contaminants may generate relatively large horizontally or/and vertically extending concentrated contaminant zones or regions, which are well known in the field and art as contaminant plumes (i.e., specific sub-surface water zones or regions concentrated with contaminants).
Limitations and Problems Particularly Relevant to Treating or Remediating Contaminated Sub-surface Water:
In particular cases where the contaminated water is a form of sub-surface water, for example, ground water, water of an aquifer, well or spring, pond, pool, or sub-surface water reservoir, which is entirely located below or beneath the ground or earth, then, there exist several limitations and problems particularly relevant to treating or remediating such contaminated sub-surface water. As stated hereinabove, practicing natural attenuation is often limited by requiring long time periods, for example, possibly up to 10,000 years, of continuous underground water flow for the various quantifiable parameters or properties of the water contaminants, and possible degradation products, to be sufficiently decreased or attenuated in the underground water. Additionally, large horizontally or/and vertically extending, and heterogeneous, concentrated contaminant zones or regions (contaminant plumes) of underground water types of water contaminants tend to be very difficult to locate, detect, characterize, and treat or remediate.
Another limitation and problem particularly relevant to treating or remediating contaminated sub-surface water concerns non-aqueous phase liquids (NAPLs), for example, trichloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride (CT). During release to the ground or earth, followed by subsequent migration into sub-surface water, the total mass of each contaminant is distributed among various sub-surface phases by diffusion of liquids and vapors. Additionally, various adsorption or/and desorption processes involving the NAPLs take place throughout sub-surface ground or earth types of geological matter (e.g., soil, sand, rocks, stones, pebbles, sediment, or/and gravel), which are typically present in the immediate environment surrounding or encompassing the contaminated sub-surface water. Dissolution of NAPLs and subsequent transport of dissolved constituents by sub-surface water generate the above described large horizontally or/and vertically extending, and heterogeneous, concentrated contaminant zones or regions (contaminant plumes).
A similar limitation and problem particularly relevant to treating or remediating contaminated sub-surface water concerns dense non-aqueous phase liquids (DNAPLs), which, because of their relatively high density and low water solubility, sink through soil and water and follow topographic lows within the sub-surface water environment, displace the lower lying sub-surface water, and accumulate upon the underlying clay stratum in the form of concentrated contaminant zones or regions (contaminant plumes). Further, since most DNAPLs are sparingly soluble in water, they are adsorbed on to sub-surface ground or earth types of geological matter, particularly soil particles, producing tenacious underground plumes of dissolved organic contaminants which cannot be readily and permanently removed by standard ‘pump and treat’ technologies.
Such sub-surface concentrated contaminant zones or regions (contaminant plumes), and residuals thereof, eventually become primary sources of sub-surface water contamination. Under natural conditions, the time required for complete dissolution or degradation of DNAPLs can be hundreds of years. Not knowing the location, characteristics, and size, of DNAPL sub-surface concentrated contaminant zones or regions (contaminant plumes), make it practically impossible to predict how long a pump and treat system must operate in order to sufficiently treat or remediate the contaminated sub-surface water. Moreover, heterogeneous, such as perched, topographies of DNAPL sub-surface concentrated contaminant zones or regions (contaminant plumes), complicate sub-surface water site investigations. It is very easy to unknowingly drill through the concentrated contaminant zone or region (contaminant plume) and the bed it sits on, causing contaminated water in the concentrated contaminant zone or region to drain down through the drilled hole into a deeper part of the sub-surface water environment, or/and into a different sub-surface water zone or region and contaminate the sub-surface water contained therein.
(c) Chemical Techniques for Treating or Remediating Water Contaminated with Halogenated Organic Compounds:
Chemical techniques for treating or remediating water contaminated with halogenated organic compounds are based on exploiting non-catalytic chemical reaction, or (homogeneous or heterogeneous) catalytic chemical reaction, types of phenomena, mechanisms, and processes, involving the use of (inorganic or/and organic) chemical reagents, for ‘chemically’ degrading, transforming, or/and converting, the halogenated organic compound water contaminants in the contaminated water to non-hazardous or/and less hazardous species.
In a non-catalytic chemical reaction type of chemical technique, at least one of the chemical reagents is a main reactant which directly reacts (without a catalyst) with the halogenated organic compound contaminant(s) in a non-catalyzed chemical reaction, typically, a redox (reduction-oxidation) chemical reaction, for degrading, transforming, or/and converting, the halogenated organic compounds in the contaminated water to non-hazardous or/and less hazardous compounds. In a homogeneous or heterogeneous catalytic chemical reaction type of chemical technique, at least one of the chemical reagents is a participant, facilitator, or expeditor, functioning as a homogeneous or heterogeneous catalyst in a homogeneous or heterogeneous catalytic chemical reaction, typically, a homogeneous or heterogeneous redox (reduction-oxidation) catalytic chemical reaction, involving the halogenated organic compound contaminant(s), for transforming, converting, or degrading, the halogenated organic compounds in the contaminated water.
Herein, for the purpose of clearly understanding, without ambiguity, the following presentation of prior art teachings, as well as of the subject matter of the present invention, a homogeneous catalytic chemical reaction is wherein the catalyst (particularly, e.g., an electron transfer mediator) is an initially solid (typically, particulate) substance that is non-supported, non-matrixed, non-intercalated, or/and non-trapped, by another material, and subsequently becomes freely mobile and soluble throughout the contaminated water. A heterogeneous catalytic chemical reaction is wherein the catalyst (particularly, e.g., an electron transfer mediator) is an initially solid (typically, particulate) substance that is supported, matrixed, intercalated, incorporated, or/and trapped, and generally immobile, on or/and inside of a (particulate or/and non-particulate) solid support or matrix material which subsequently becomes dispersed (i.e., not dissolved) throughout the contaminated water. Ordinarily, the initially immobilized catalyst similarly becomes dispersed (i.e., not dissolved) throughout the contaminated water, but, may at least partially dissolve in the contaminated water, depending upon actual parameters and conditions of a given heterogeneous catalytic chemical reaction system.
Chemical Destruction (with Chemical Reagents):
Chemical destruction (with chemical reagents), as an exemplary chemical technique for treating or remediating contaminated water, is based on using ‘destructive’ chemical reagents (e.g., strong chemical oxidizers), under existing conditions of temperature or/and pressure, or, alternatively, under machine generated extreme or destructive conditions of temperature or/and pressure, for breaking chemical bonds of the water contaminants, for the objective of destroying the water contaminants. Destruction of the water contaminants may involve degrading, transforming, or/and converting, the water contaminants to non-hazardous or/and less hazardous species.
A first significant limitation of using the technique of chemical destruction (with chemical reagents) for treating or remediating contaminated water is that use of the destructive chemicals can be difficult, potentially hazardous, and expensive, to apply to large (areal or/and volumetric) scale forms of contaminated water. A second significant limitation of this technique is that the types or kinds of destructive chemicals which are required for being sufficiently effective in destroying the water contaminants are usually non-specific, whereby their use may be accompanied by undesirable consequences, such as partial or complete change of the immediate environment or ecosystem, and geological matter present therein, surrounding or encompassing the form of contaminated water being treated. This is particularly problematic if the form of contaminated water is surrounded or encompassed by a naturally existing environment or ecosystem. For example, the destructive chemical reagents used for degrading, transforming, or/and converting, the water contaminants to non-hazardous or/and less hazardous species, may themselves be hazardous or/and potentially hazardous, or/and may introduce hazardous or/and potentially hazardous conditions, in the immediate environment or ecosystem, and geological matter present therein, surrounding or encompassing the form of contaminated water being treated.
Reductive Dehalogenation:
Currently, most chemical techniques used for treating or remediating water contaminated with halogenated organic compounds are based on reductive dehalogenation (typically, dechlorination) types of non-catalytic or (homogeneous or heterogeneous) catalytic, redox chemical reactions, phenomena, mechanisms, and processes, involving the use of (organic or/and inorganic) chemical reagents, for ‘chemically’ dehalogenating (dechlorinating) the halogenated organic compounds in the contaminated water. In general, reductive dehalogenation involves transfer of a number of electrons (ne−), either in the absence or presence of a catalyst (such as an electron transfer mediator type catalyst), from a bulk electron donor or reducing agent (being any of a wide variety and combinations of numerous possible organic or/and inorganic chemicals (for example, naturally existing in, originating from, or synthetically derived from, mineral matter, plant matter, or biological matter)), to an electron acceptor, being the halogenated (typically, chlorinated) organic compound contaminant ([R—X]; X=halogen, typically, chlorine [Cl]). The reductive dehalogenation chemical reaction is a form of (non-catalytic or catalytic) hydrogenolysis whose general scheme (without or with a catalyst) is indicated by chemical equation (1), wherein Y+ is a proton [H+] or any other positively charged atom or moiety:R—X+ne−+Y+→R—Y+X−  (1)
Phytochemical Reductive Dehalogenation For Treating or Remediating (Phytoremediating) Water Contaminated with Halogenated Organic Compounds:
A first exemplary type of reductive dehalogenation for treating or remediating water contaminated with halogenated organic compounds is based on phytochemistry (plant chemistry). Phytochemical types of reductive dehalogenation (typically, dechlorination) non-catalytic or catalytic redox chemical reactions, involving the use of aquatic or terrestrial plants or plant derived chemicals as the bulk electron donors or reducing agents, for ‘phytochemically’ dehalogenating (dechlorinating) or ‘phytodegrading’ various different kinds of halogenated organic compounds in contaminated or polluted water, have been well studied [e.g., 4-8].
Zero Valent Metal (ZVM) Reductive Dehalogenation for Treating or Remediating Water Contaminated with Halogenated Organic Compounds:
A second exemplary type of reductive dehalogenation for treating or remediating water contaminated with halogenated organic compounds is based on the use of elemental metal or a zero valent metal (ZVM). The zero valent metal (ZVM) reductive dehalogenation (typically, dechlorination) technique is generally based on exposing water contaminated with halogenated organic compounds to a bulk quantity of granular or/and powdered elemental metal particles in the metallic or zero valent state, during which the contaminants are degraded, transformed, or/and converted, to non-hazardous or/and less hazardous species, or/and are immobilized on the surface of the metal particles, for example, by adsorption or/and precipitation processes. Typically, exposing the contaminated water to the zero valent metal particles is performed in a manner, for example, under reducing (anaerobic or anoxic) conditions, such that only contaminant species in the contaminated water, and not non-contaminant species (such as oxygen gas) in the contaminated water or/and in the immediate vicinity of the contaminated water, are reduced by the zero valent metal particles.
The general mechanism of zero valent metal (ZVM) reductive dehalogenation involves a two-electron transfer which occurs either directly on the metal surface, or/and through some intermediary (catalyst), in particular, depending upon the absence or presence of a catalyst, from the bulk electron donor or reducing agent (which becomes oxidized), to the halogenated organic compound contaminant ([R—X]; X=halogen, typically, chlorine [Cl]) as the electron acceptor, thereby reducing the halogenated organic compound contaminant, for example, to a reduced form [R—H], as generally indicated by chemical equation (2), wherein Y+ is a proton [H+] or any other positively charged atom or moiety:R—X+M0+Y+→M2++R—Y+X−  (2)
Although different elemental or zero valent metals, for example, iron [Fe0], cobalt [Co0], nickel [Ni0], copper [Cu0], and zinc [Zn0], are applicable, zero valent iron [Fe0] (ZVI) is most commonly used for implementing the ZVM technique. The zero valent metal reductive dehalogenation process has been known for years, however, only during the past decade has the use of ZVM, in general, and ZVI, in particular, become accepted as one of the most effective means of sub-surface water (e.g., ground water, aquifer water) remediation. ZVI particles are relatively inexpensive, and reasonably effective for in-situ or ex-situ catalytically reducing concentrations of a wide variety of different types of water contaminants, such as organic species, for example, halogenated organic compounds and halogen containing degradation products thereof, and inorganic species, for example, metal elements, metal element containing inorganic species, and oxygen containing inorganic species (e.g., oxygen containing ions (oxyions, or oxo-anions), such as borate ions, nitrate ions, sulfate ions, phosphate ions, halogenate ions (i.e., containing a halogen), and metal oxide ions).
In particular cases where the contaminated water is a form of sub-surface water, for example, ground water, water of an aquifer, well or spring, pond, pool, or sub-surface water reservoir, then, in actual field applications, the ZVM technique is typically implemented by placing a bulk quantity of granular or/and powdered zero valent metal (ZVM) particles, alone or with other reactive or/and inactive materials, in a sub-surface permeable reactive barrier (PRB). A sub-surface permeable reactive barrier (PRB) is a closed or open structure or configuration, such as a filled in trench, wall, or well, or a system of several closed or/and open structures or configurations, that provides passive interception and in-situ treatment of contaminated sub-surface water (e.g., ground water, aquifer water). A sub-surface permeable reactive barrier is characterized by having a permeable zone containing or creating a reactive treatment area, including a highly reactive material, for example, ZVM particles, and optionally, also including a less reactive, an inactive, or/and a non-reactive material, oriented to intercept and remediate or purify a sub-surface water (e.g., ground water, aquifer water) contaminant plume (i.e., a specific sub-surface region or zone concentrated with contaminants), by direct exposure of the water contaminants to the reactive material.
Ideally, a sub-surface permeable reactive barrier provides a preferential flow path of the contaminated sub-surface water (e.g., ground water, aquifer water) through the reactive material, and the other possibly present materials, and degrades, transforms, or/and converts, the water contaminants into environmentally acceptable (non-hazardous or/and less hazardous) species which exit the barrier, while minimally disrupting natural flow of the sub-surface water (e.g., ground water, aquifer water). Typically, the contaminated sub-surface water (e.g., ground water, aquifer water) flows by natural flow (pressure or current) gradients through the sub-surface PRB, however, pumping schemes configured upstream, within, or/and downstream, the sub-surface PRB, can also be used for implementing a sub-surface PRB setup. A sub-surface PRB can be installed as a permanent or semi-permanent closed or open structure or configuration spanning along or/and across the flow path of a sub-surface water contaminant plume. Alternatively, a sub-surface PRB can be installed as a construction or configuration as part of an in-situ reactor which is readily accessible to facilitate the removal or/and replacement of the spent (deactivated) reactive zero valent metal material, and the other possibly present materials.
There are extensive prior art teachings [e.g., 9-16] about the ZVM technique, typically involving use of zero valent iron (ZVI) in non-catalytic reaction systems, for non-catalytically reductively dechlorinating chlorinated organic solvents, such as carbon tetrachloride (CT) [C(Cl)4], dichloroethylene (dichloroethene) (DCE) [C2H2Cl2], trichloroethylene (trichloroethene) (TCE) [C2HCl3], perchloroethylene (PCE) (tetrachloroethylene, tetrachloroethene) [C2Cl4], among many others, which are of significant environmental concern.
Electron Transfer Mediators as Catalysts of Reductive Dehalogenation Reactions:
An active area in the field of environmental science and technology, focusing on treating or remediating water contaminated or polluted with halogenated organic compounds, concerns the use of electron transfer mediators for (homogeneously or heterogeneously) catalyzing reductive dehalogenation (typically, dechlorination) of halogenated organic compounds under reducing (typically, anaerobic or anoxic) conditions.
Electron transfer mediators are chemical substances, functioning as catalysts or co-catalysts, which are catalytically active, and expedite (catalyze) redox (reduction-oxidation) types of chemical reactions, such as reductive dehalogenation, by participating in, mediating, and expediting, the transfer of electrons from a bulk electron donor or reducing agent to an electron acceptor, or/and by stabilizing intermediate forms of the redox reactants. An electron transfer mediator which specifically functions by participating in, mediating, and expediting, the transfer of electrons from a bulk electron donor or reducing agent to an electron acceptor is also known as an electron carrier or as an electron shuttle, since electrons are carried and shuttled by such a chemical species.
Based on the above described general mechanism of reductive dehalogenation, along with reference to chemical equation (1), the general mechanism of an electron shuttle type of reductive dehalogenation system which includes an electron transfer mediator type catalyst is as follows. Under reducing conditions, in the presence of an electron transfer mediator type catalyst, the bulk electron donor or reducing agent transfers the electrons (ne−) to an electron transfer mediator molecule, which becomes reduced, during which the bulk electron donor or reducing agent becomes oxidized. The reduced electron transfer mediator molecule then carries (shuttles) and transfers the electrons to a halogenated organic compound contaminant [R—X] electron acceptor, which becomes reduced [R—Y], during which the electron transfer mediator molecule becomes oxidized. The oxidized electron transfer mediator molecule is then reduced again by the bulk electron donor or reducing agent, thus enabling the electron transfer mediated catalytic reductive dehalogenation cycle to repeat.
Numerous laboratory studies [e.g., 17-22] have shown that reductive degradation, transformation, or/and conversion, of certain relatively oxidized organic compounds (such as halogenated organic compounds) can be expedited (i.e., catalyzed) by use of electron transfer mediator type catalysts in electron shuttle systems.
In general, electron shuttle systems involve the use of naturally occurring organic macrocycles complexed with transition metals, as electron transfer mediators, to carry and shuttle electrons from the bulk electron donor or reducing agent to the electron acceptor, thereby reductively degrading, transforming, or/and converting, the electron acceptor (halogenated organic compound). These relatively simple laboratory abiotic (but biomimetic) systems typically exhibit faster reaction rates relative to systems utilizing direct biological reduction reactions. Several naturally occurring biogeochemical substances, such as mineral substances, naturally occurring organic matter (NOM), bacterial transition metal coenzymes, and other biomimetic macrocycles, have been proposed and studied for use as electron transfer mediator type catalysts [e.g., 17, 20; 23-29].
Prior art also includes various teachings of such electron transfer mediated catalytic reductive dehalogenation reaction systems, where the electron transfer mediator type catalyst is a humic substance [e.g., 30-32]; a quinone [e.g., 33]; or a protein [e.g., 28].
Porphyrinogenic Organometallic Complexes (Electron Transfer Mediator Catalytic Functionality):
The term ‘porphyrinogenic organometallic complex’ refers to an organometallic complex formed between a neutral metal atom or a metal ion and a porphyrinogenic or porphyrinogenic-like ring system, and is further defined and exemplified hereinbelow in the Description of the present invention.
Metalloporphyrin complexes (commonly known and referred to as metalloporphyrins), being porphyrinogenic organometallic complexes of metal ions and porphyrin ligands, are organic tetrapyrrole macrocycles composed of four pyrrole type rings joined by methane (methylidene) bridges and complexed to a central metal ion. They form a near planar structure of aromatic macrocycles containing up to 22 conjugated π electrons, 18 of which are incorporated into the delocalization pathway in accordance with Huckel's [4n+2] rule of aromaticity. One or two of the peripheral double bonds of the porphyrin ligands of a metalloporphyrin can undergo an addition reaction to form a metalloporphyrin derivative, such as a metallocorrin or a metallochlorin type of porphyrinogenic organometallic complex.
There are extensive teachings [e.g., 34] about the origin, and the numerous physical, chemical, and biological, properties, characteristics, and behavior, of porphyrinogenic organometallic complexes, of which thousands have been identified and studied [e.g., 35, 36]. Exemplary well known metalloporphyrin complexes are chlorophylls, which are magnesium (II) complexes; hemes, which are iron (II) complexes; and cytochromes (e.g., cytochrome P450, and cytochrome P430) Vitamin B12 (cyanocobalamin) a naturally occurring, or synthesized, metalloporphyrin-like complex of related structure and function, is a metallocorrin type of porphyrinogenic organometallic complex composed of a corrin ligand (a porphyrin analog in which some of the methylene bridges are substituted or/and absent) complexed to a cobalt (III) ion.
Porphyrinogenic organometallic complexes, such as metalloporphyrins, metalloporphyrin-like complexes, and their derivatives, exist in many biochemical environments, such as living cells, soils, sediments, bitumens, coal, oil shales, petroleum, and other types of naturally occurring deposits rich in organic matter [e.g., 37-39]. Porphyrinogenic organometallic complexes are well known for functioning as electron transfer mediators, and play an important role in various biochemical pathways, such as oxygen transport and storage (hemoglobin and myoglobin, respectively) and electron transfer in redox (reduction-oxidation) reactions (cytochromes).
Porphyrinogenic organometallic complexes exhibit several particular properties, characteristics, and behavior, which make them especially well applicable for functioning as electron transfer mediator type catalysts in homogeneous or heterogeneous electron transfer mediated catalytic reductive dehalogenation (typically, dechlorination) reaction systems, for catalyzing reductive dehalogenation of halogenated organic compound contaminants in water under reducing (anaerobic or anoxic) conditions. Porphyrinogenic organometallic complexes are: (1) effective redox catalysts for many reactions, and have a long range of redox activity; (2) electrochemically active with almost any core metal; (3) active catalysts in aqueous solution under conditions particularly pertinent to environments of various different forms of contaminated sub-surface water and surface water; and (4) relatively highly stable, thereby enabling reactions to take place under severe conditions, where other types of reactions probably would not take place.
Porphyrinogenic organometallic complexes, such as metalloporphyrins and metalloporphyrin-like complexes, are well known for being used as electron transfer mediator type catalysts in homogeneous catalytic reduction processes. There are numerous prior art teachings [e.g., 17-22; 40-51] about electron transfer mediated homogeneous catalytic reductive dehalogenation (typically, dechlorination) reaction systems, involving the use of various different porphyrinogenic organometallic complexes as homogeneous electron transfer mediator type catalysts (i.e., an initially solid (typically, particulate) substance that is non-supported, non-matrixed, non-intercalated, or/and non-trapped, by another material, and subsequently becomes freely mobile and soluble throughout the contaminated water), for homogeneously catalyzing reductive dehalogenation of halogenated organic compounds, such as halogenated organic solvents or other non-herbicide type halogenated organic compounds, particularly those which are known problematic contaminants or pollutants in water. In the above cited prior art, halogenated (chlorinated) organic compounds most extensively and frequently studied are: chlorinated methanes, chlorinated ethanes, chlorinated ethylenes (ethenes), chlorinated phenols (chlorophenols), and polychlorinated biphenyls (PCBs).
There are also prior art teachings [e.g., 8] of using hematin (reduced form of the porphyrin heme), or the metalloporphyrin hemoglobin, as an electron transfer mediator type catalyst, in the presence of dithionite (hydrosulfite) [S2O4−2] as a bulk electron donor or reducing agent, for homogeneous catalytic reductive dehalogenation (dechlorination) and degradation, in aqueous solutions, of various enantiomeric forms and analogs of the (bridged diphenyl) halogenated organic compound DDT (p,p′-DDT) (DichloroDiphenylTrichloroethane) [C14H9Cl5], historically well known as an extremely hazardous water contaminant.
Electron Transfer Mediators as Catalysts in Heterogeneous Composites, for Reductive Dehalogenation:
Studies have shown that porphyrinogenic organometallic complexes, such as metalloporphyrins, can be incorporated (via intercalation) and immobilized on or/and in layered minerals, or amorphous silica gel surfaces, for forming heterogeneous composites that can be used for heterogeneously catalyzing electron transfer mediated reactions. For example, heterogeneous composites composed of the cobalt metalloporphyrin, tetramethylpyridilporphyrin [5, 10, 15, 20-tetrakis(1-methyl-4-pyridinio)-porphine-cobalt] [TMPyP-Co], incorporated on or/and in silica gel and double-layered clays were used for heterogeneously catalyzing reductive dechlorination of carbon tetrachloride [CCl4] in water [52]. Prior art [e.g., 53] also includes teachings about incorporating and immobilizing metalloporphyrins on or/and in sepharose, sephadex, or polystyrene, types of solid support or matrix materials, for forming heterogeneous composites that can be used for heterogeneously catalyzing electron transfer mediated reductive dechlorination reactions.
Diatomite (Diatomaceous Earth, Kieselguhr):
Diatoms (bacillariophyceae) are microscopic, about 1 to 500 μm sized, unicellular algae found in both freshwater and marine environments. These single-celled plants develop external, amorphous silica skeletons (frustules) possessing pores having sizes on the order of nanometers. These pores are uniform in diameter, with dimensions that are species specific. The smallest of these pores have diameters in the range of about 20 to 200 nm. The structure of a diatom is similar to that of a pillbox. The siliceous shell or ‘test’ is made of opaline silica (SiO2.nH2O). Diatoms are found in fresh, salt, or brackish, water, wherein many species are found floating in the surface layers of the water, although the majority are benthic, ‘floor dwelling’ species.
Diatomite, also known as diatomaceous earth or kieselguhr, is a porous, chalk-like, sedimentary rock, formed by fossil accumulation of diatoms in the form of amorphous, hydrated silica. Diatomite is highly absorbent, physically and chemically stable, nearly indestructible, and ordinarily chemically inert to most common water contaminants. Diatomite is readily crushed or/and physically processed into a powdered form, and sieved into specific average particle size ranges according to particular applications.
Due to the ability of diatomite to absorb its own weight in liquid, its major uses are as absorbent materials and industrial filters. Diatomite is used in a variety of food production applications, such as clarification and filtration of beer and wines, refining sugar and sweeteners, and, filtering fruit juices, oils, and syrups. Heavier industry uses diatomite filters for filtration and stabilization of pharmaceuticals, serums, and other pharmaceutical and biotechnology applications, and chemicals that include liquid acids and other liquid wastes. The porous characteristic of diatomaceous earth allows industries to exploit this quality and use it as an absorbent for gases, noxious materials, soluble fertilizing agents, sealing wax, pasteboard, rubber erasers, and, fatty and acidic materials. Diatomite is also used as a filler, to ‘bulk out’ finished manufactured products, as it is ordinarily non-reactive. Such products are paints, lacquers, rubbers, plastics, polishes, agricultural chemicals (agrochemicals), insulation, anti-caking agent, cement, concrete, animal feeds, and fertilizers. Diatomite is also well known and widely used as a non-reactive or minimally reactive support, substrate, carrier, matrix, or dispersing agent, material, singly, or in combination with other similar types of materials, for heterogeneous catalysts, including, for example, ZVM types of catalysts.
Vermiculite:
Vermiculite is the mineralogical name given to any of a group of micaceous hydrated silicates of varying composition, related to the chlorites. Vermiculite exfoliates or expands upon heating. In the exfoliated or expanded state, vermiculite has many applications in a wide variety of different types of fields and industries, such as horticulture and agriculture. Among the many applications, vermiculite is commonly used in the horticultural and botanical industries because it provides both aeration and drainage, it retains and holds substantial amounts of water and later releases it as needed, it is sterile and free from diseases, it has a fairly neutral pH, and it is readily available, non-toxic, safe to use, and relatively inexpensive.
Several specific horticultural and botanical applications involving the use of vermiculite are blocking mixes, hydroponics, micro-propagation, potting mixes, rooting cuttings, seed germination, seedling wedgemix, sowing composts, and twin scaling bulbs. Several specific agricultural applications involving the use of vermiculite are animal feeds, anti-caking materials, bulking agents, fertilizers, pesticides, seed encapsulants, and soil conditioners. Additional industrial applications involving the use of vermiculite are absorbent packing materials, dispersions, drilling muds, filtration, fixation of hazardous materials, and nuclear waste disposal. Vermiculite is also used as a filler, to ‘bulk out’ finished manufactured products, as it is ordinarily non-reactive. Vermiculite is also known and used as a non-reactive or minimally reactive support, substrate, carrier, matrix, or dispersing agent, material, singly, or in combination with other similar types of materials, for heterogeneous catalysts. Due to its chemical composition including the presence of Fe+2, vermiculite has been reported to be an active compound in the reduction of halogenated (e.g., chlorinated) organic compounds present in contaminated water.
Although there exists a plethora of numerous different types of well known and used prior art techniques (methods, materials, compositions, devices, and systems) for treating or remediating contaminated water, there remains on-going need for improving current techniques, as well as for identifying, developing, and implementing, new techniques, for example, with respect to techniques based on the use of zero valent metal materials, for treating or remediating contaminated water. Accordingly, new, technologically and economically feasible, and effective treatment and remediation techniques need to be developed and implemented in order to meet stringent water quality standards, and to reduce environmental and health risks associated with pervasive (widespread), persistent (e.g., having half-lives ranging from days to 10,000 years), proven or potentially hazardous (poisonous or toxic), undesirable contaminants in various forms of water, especially such forms of water which are, or/and come in direct contact with, or/and lead to, sources of drinking water.
There is thus a need for, and it would be highly advantageous to have a zero valent metal composite, a method for manufacturing thereof, a method using thereof, a system including thereof, and an article-of-manufacture including thereof, wherein the zero valent metal composite is used for (in-situ or ex-situ) catalytically treating contaminated water. Moreover, there is a need for such an invention which is generally applicable to (in-situ or ex-situ) catalytically treating any of a wide variety of different forms of contaminated water, for example, sub-surface water, surface water, above-surface water, water vapor, gaseous water, or any combination thereof, which are contaminated with any number of a wide variety of different types or kinds of organic or/and inorganic chemical contaminants. Furthermore, there is a need for such an invention which is particularly applicable to (in-situ or ex-situ) catalytically treating such forms of contaminated water wherein the water contaminants are organic species, for example, halogenated organic compounds and halogen containing degradation products thereof; inorganic species, for example, metal elements, metal element containing inorganic species, nonmetal elements, and nonmetal element containing inorganic species; or any combination thereof.